Meeting Abstract
The evolutionary origin of complex adaptive traits has been a controversial topic in the history of evolutionary biology. Although Darwin argued for the gradual origins of complex adaptive traits within the theory of natural selection, Mivart insisted that natural selection could not account for the incipient stages of complex traits. The debate starting from Darwin and Mivart eventually engendered two opposite views: gradualism and saltationism. Although this has been a longstanding debate, the issue remains unresolved.
Here I review recent findings as a starting point to propose the building logic of complex traits. First, I report that previous studies have already revealed the gradual evolution of several valuable traits (e.g., the giraffe’s elongated neck, the asymmetrical eyes of flatfishes, whale baleen, and butterfly leaf wings), which could be explained within the theory of natural selection. Through such a comprehensive survey, I found that these traits satisfy two important characteristics: (1) reducibility into a sum of subcomponents; (2) composability to construct traits from various additional and combinatorial arrangements of the subcomponents. I thus propose the building logic of complex traits, named as reducible-composable multicomponent (rcMC) systems (ref. 1). On the basis of this, I developed an analytical method for exploring evolutionary pathways to build up complex traits, by using component-based phylogenetic comparative methods (c-PCMs) based on Bayesian statistics. I used this method and succeeded in revealing gradual evolution of leaf mimicry in Kallima butterfly wings (ref. 2). Finally, I use butterfly camouflage patterns and discuss how to decipher structural complexity of morphological traits.
References:
1. Suzuki (2017) J Exp Zool B 328(4): 304–320.
2. Suzuki, Tomita, Sezutsu (2014) BMC Evol Biol 14:229.
